Stabilized iron pentacarbonyl and motor fuel containing the same



Patented Jan. 3, 1950 UNITED STATES PATENT OFFICE STABILIZED IRON PENTACARBONYLI AND MOTOR FUEL CONTAINING rm: SAME No Drawing. Application May 21, 1946, Serial No. 671,399

16 Claims.

This invention relates to liquid fuels suitable for use in internal combustion engines. More particularly, it relates to the use of iron pentacarbonyl as an anti-knock agent in motor fuels and to iron pentacarbonyl of improved stability to light and air.

It is known that iron pentacarbonyl possesses the property of raising the octane value of gasoline. It is ideal in many respects as an antiknock, a very small amount, less than 0.1% by volume, being suiiicient to raise the octane rating of gasoline to a high value. It is very soluble in gasoline, substantially inert with respect to the parts of the engine with which it comes in contact, and in concentrated or diluted form does not cause poisoning on contact with the skin.

Despite its many advantages, iron pentacarbonyl, Fe(CO) 5, has not attained commercial success as an anti-knock agent due to its inherent instability to light by which it is rapidly decomposed, this decomposition being most rapid in sunlight or blue light and least so in red light. The decomposition is a progressive change, the first product being iron enneacarbonyl, Fe2(CO)9, which comes down in the form of glistening golden-yellow plates according to the following reaction,

followed by a further decomposition with production of a voluminous black precipitate of ferrous oxide and other iron compounds.

This decomposition not only results in loss of octane value from the initially high level obtained in the gasoline with the freshly dissolved iron pentacarbonyl but also renders the gasoline unfit as a motor fuel due to the propensity of the pre-, cipitate to clog the gasoline line or the carburetor.

I have now found that motor fuels of high quality, which in the presence of sunlight and air exhibit a high degree of permanency in respect to anti-knock characteristics and. freedom from formation of precipitates derived from the antiknock agent, may be obtained from gasoline of low octane value and iron pentacarbonyl by employing in conjunction with the latter certain substances, hereinafter more particularly defined, which act as stabilizers for the iron pentacarbonyl.

The present invention resides in my discovery that iron pentacarbonyl may be rendered substantially permanently resistant to decomposition by light and air when there is intimately associated therewith a hydrocarbon-soluble substance which is a saturated aliphatic hydroxy polycarboxylic acid neutral aliphatic ester-aliphatic amide free from acidic groups, acidified with a hydrocarbon-soluble carboxylic acid.

The term neutral as used herein with reference to the ester-amides is employed in the usual sense to denote that all of the carboxyl groups of the hydroxy polycarboxylic portion of the ester-amide molecule are in the form of a mixture of ester and amido groups, none being in the free state.

For the acidification of the neutral esteramides, the amount of the hydrocarbon-soluble carboxylic acid generally need not exceed a volume equal to that of the neutral ester-amide, only suflicient being employed to bring about the acidification. A preferred group ofacids for this purpose are the long chain fatty acids, for example, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, ricinoleic acid, etc. Naphthenic acids as obtained from the oxidation of petroleum, Fischer- Tropsch acids and rosin acids also may be used.

For improving the stability of the iron pentacarbonyl to light and air, the acidified neutral ester-amides may be employed in widely varying amounts, ranging from about 1% to about 50% by volume on the iron pentacarbonyl. The amount necessary in each instance to render the iron pentacarbonyl substantially permanently.

stable to light and air may vary with the individual acidified neutral ester-amides, but, in general, it will be about 5 to 10% by volume on the iron pentacarbonyl.

In the practice of the invention for the preparation of motor fuels of increased anti-knock characteristics the iron pentacarbonyl, which is a liquid, and the stabilizer are simply dissolved in the gasoline or other liquid base fuel to be treated, the mixture being stirred to insure uniformity in dispersion of the iron pentacarbonyl and the stabilizer therein. The iron pentacarbonyl, itself, is employed in amounts of 1 to 4 cc. or more per gallon of the liquid motor fuel, a preferred proportion based on a gasoline of -65 octane number being from 3 to 4 cc. per gallon of the gasoline. It will be understood, of course, that the proportion of iron pentacarbonyl used will depend on the initial octane value of the liquid fuel to be treated and as well on the level to which this value is to be lifted by the treatment. Generally, the lower the octane rating of the liquid fuel, the greater should be the proportion of iron pentacarbonyl added thereto.

The iron pentacarbonyl and stabilizer may be added separately to the liquid fuel or, as is preferred, they are added together from a concentrate which is a blend of the. iron pentacarbonyl, the stabilizer, and a small proportion of a mutual ,organic solvent therefor which is compatible as an ingredient of the liquid motor fuel. suitably, a portion of the liquid fuel of the kind to be treated.

' The stabilized concentrate may be stored over long sene, benzol or other solvent appropriate to the motor fuel and then adding the iron pentacarbonyl to this solution with stirring to eflect a homogeneous mixture. A suitable proportion of solvent and iron pentacarbonyl in the concen-' trates is about equal volumes of the two, although this proportion maybe varied somewhat where particular concentrations of iron pentacarbonyl are desired.

The motor fuels which may be treated with the stabilized anti-knock agent for improvement in octane value may be-any of the usual liquid hydrocarbon fuels such as kerosene, gasolines, straight-run, cracked or so-called "poly gasoline, or blends of these with benzol, alcohol or the like, Diesel fuels of the Flscher-Tropsch type, or other types, such as alcohols, in which the iron pentacarbonyl and stabilizer are soluble.

By the term hydrocarbon-soluble as used herein is meant that the substance so-designated is soluble in kerosene, gasoline, benzol and the like liquid hydrocarbons.

As a specific: example of stabilized anti-knock 'concentrates which may be prepared in accordance with the invention is the following composition in which was blended in the preferred manner, by volume,

1 part neutral ester-amide of malic acid from oleyl alcohol and oleylamine Y 1 part stearic acid 22 parts gasoline parts iron pentacarbonyl When mixed with a gasoline of octane number 65 in the proportion of 8.8 cc. to the gallon of gasoline, the mixture represents a motor fuel of 75 octane number which retains its high antiknock quality over long periods of time on exposureto air or sunlight.

Further illustrative of the neutral ester-amides which in conjunction with a hydrocarbon-soluble carboxylic acid may be employed in accordance with the invention for improving the stability of iron pentacarbonyl to light and air are, for example, the hydrocarbon-soluble neutral aliphatic ester-aliphatic amides of l-hydroxy glutaric acid, Z-hydroxy glutaric acid, 2-hydroxy glutamic acid, l-hydroxy adipic acid, 4-hydroxy azelaic acid, 2-ethyl malic acid, malic acid, tartronic acid, tartaric acid, citric acid, isocitric acid, hydroxy citric acid, l-hydroxy- 1 carboxysuccinic acid, l-hydroxybutane-l,2,3-tricarboxylic acid, 3-hydroxybutane-1,1,5-tricarboxylic acid, 2-hydroxy-4 methyipentane-1,l,2,4-tetracarboxylic acid and 1,G-dihydroxyhexane-2,2,55-

tetracarboxylic acid, etc., or of mixtures of these acids, where the ester group or groups are derived from an aliphatic monohydric alcohol, the alkyl radical of which has at least four carbon atoms" and may contain substituents which do not give riseto corrosive fumes in the engine on combustion of the motor fuel, suchas chlorinev and bromine atoms, for example, 2-ethylbutanol, methyl amyl alcohol, hexanoi, heptanol- 2,2-ethylhexanol, undecanol, dodecanol, tetradecanol, heptadecanol, octadecanol, oleyl alcohol, cyclohexyl alcohol, 2-ami'no-butanoi-l, -iamino-butanol-l, tertiary butyl alcohol, etc., and the amide group or groups from a primary or secondary aliphatic amine, the alkyl radical of which has at least four carbon atoms and, likewise, may contain substituents of the kind indicated in respect to the monohydric alcohols, ante, for example, n-dibutylamine, 2-ethylhexylamine, di-2 ethyl hexylamine, dodecylamine, tetradecyiamine, hexadecylamine, octadecylamine, .cyclohexylamine, fl-chlorobutylamine, bromobutyiamine, p-ethoxy-butylamine, etc.

Preferably, these ester and amide groups of the neutral ester-amides contain the longer chain hydrocarbon radicals, for example, of about 8 or more carbon atoms in the case of the ester groups and of about 10 or more carbon atoms in the case of the amido groups, as the longer the hydrocarbon chain thereof, generally the greater the hydrocarbon solubility of the neutral esteramide molecule.

The neutral aliphatic ester-aliphatic amides may be prepared in any manner found suitable. Following known procedure (Karrer, Organic Chemistry, New York 1938, page 199) they may be prepared from the corresponding neutral esters of the saturated aliphatic hydroxy polycarboxylic acids by heating the neutral-ester with a solution of the amine taken in quantity suffl-.

cient to replace a part onlyjof the ester groups.

For example, malic-acid neutral oleylester-oleylamide may be prepared by heating one moleof malic acid trioleylester with a solution of one mol of oleylamine. The tri-esters of the hydroxy carboxylic acids may be prepared in known way for the esterifi'cation of carboxylic acids. Obviously, the temperature to which the reactants are heated should be below that at which dehydration of the hydroxy'carboxylic compound occurs through loss therefrom of the alcoholic hydroxy group. A preferred group of the hydroXy polycarboxylic acids for the preparation of the neutral aliphatic ester-aliphatic amides are citric, malic, tartaric and tartronic acids, preferred; however, only from, the standpoint of ready availability from natural sources.

In addition to their action as stabilizers for the iron pentacarbonyl in the motor fuel, the

herein-defined acidified neutral aliphatic esteraliphatic amides favorably influence the removal of the residue of the iron pentacarbonyl from the internal combustion engine. In this respect it has been observed that the residue is almost completely removed from the combustion areas of the engine and emerges from the exhaust as a light, flufiy red powder.

As various other embodiments of the invention will occur to those skilled in the art, it is not intended that the scope of the patent be limited except as is required by the prior art and the appended claims.

I claim:

1. A composition comprising iron pentacarbonyl blended with from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester-alkylamide of a saturated aliphatic hydroxy polycarboxylic acid in which the hydroxy portion is free and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms, the alkylester-alkylamide bein acidified with no more than an equal volume of a hydrocarbon-soluble carboxylic acid.

2. A composition comprising iron pentacarbonyl blended with from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester-alkylamide of citric acid in which the hydroxy portion is free and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms, the alkylester-alkylamide being acidified with no more than an equal volume of a hydrocarbon-soluble carboxylic acid.

3. A composition comprising iron pentacarbonyl blended with from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester-alkylamide of malic acid in which the hydroxy portion is free and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms, the alkylester-alkylamide being acidified with no more than an equal volume of a hydrocarbon-soluble carboxylic acid.

4. A composition comprising iron pentacarbonyl blended with from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester-alkylamide of tartaric acid in which the hydroxy portion is free and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms, the alkylester-alkylamide being acidified with no more than an equal volume of a hydrocarbon-soluble carboxlic acid.

5. A composition comprising iron pentacarbonyl blended with from about 1 to about 50% by volume on the pentacarbonyl of malic acid neutral oleylester-oleylamide acidified with a volume of a long chain fatty acid not exceeding that of the malic acid neutral oleylesteroleylamide.

6. A motor fuel comprising a liquid base fuel in which is dissolved a minor proportion of iron pentacarbonyl and from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester-alkylamide of a saturated aliphatic hydroxy polycarboxylic acid in which the hydroxy portion is time and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms, the alkylester-alkylamide being acidified with no more than an equal volume of a hydrocarbon-soluble carboxylic acid.

7. A motor fuel comprising a liquid hydrocarbon fuel in which is dissolved a minor proportion of iron pentacarbonyl and from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester-alkylamide of a saturated aliphatic hydroxy polycarboxylic acid in which the hydroxy portion is free and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms, the alkylesteralkylamide being acidified with no more than an equal volume of a hydrocarbon-soluble carboxylic acid.

8. A motor fuel comprising a liquid hydrocarbon fuel in which is dissolved a minor proportion of iron pentacarbonyl and from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester-alkylamide of citric acid in which the hydroxy portion is free and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms, the alkylester-alkylamide being acidified with no more than an equal volume of a hydrocarbon soluble carboxylic acid.

9. A motor fuel comprising a liquid hydrocarbon fuel in which is dissolved a minor proportion of iron pentacarbonyl and from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester-alkylamide of malic acid in which the hydroxy portion is free and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms, the alkylester-alkylamide being acidified with no more than an equal volume of a hydrocarbonsolubie carboxyllc acid.

10. A motor i'uel comprising a liquid hydrocarbon fuel in which is dissolved a minor proportion of iron pentacarbonyl and from about l to about 50% by volume on the pentacarbonyl oi. an acidified hydro-carbo'n-soluble neutral alkylester-alkylamide of tartaric acid in which the hydroxy portion is free and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms, the alkylester-alkylamide being acidified with no more than an equal volume of a hydrocarbonsolubie carboxylic acid.

11. A motor fuel comprising a liquid hydrocarbon fuel in which is dissolved a minor proportion of iron pentacarbonyl and from about 1 to about 50% by volume on the pentacarbonyl oi malic acid neutral oleylester-oleylamide acidified with a volume of a long chain fatty acid not exceeding that of the malic acid neutral oleyl= ester-oleylamide.

12. A stabilized iron pentacarbonyl concentrate consisting essentially of iron pentacarbonyl, from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester-alkylamide of a saturated aliphatic hydroxy polycarboxylic acid in which the hydroxy portion is free and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms, the alkylester-alkylamide being acidified with no more than an equal volume of a hydrocarbonsoluble carboxylic acid, and an amount of a liquid hydrocarbon solvent suflicient to dissolve the pentacarbonyl and the acidified alkylesteralkylamide.

13. A stabilized iron pentacarbonyl concentrate consisting essentially of iron pentacarbonyl, from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester-alkylamide of citric acid in which the hydroxy portion is free and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms, the alkylester-alkylamide being acidified with no more than an equal volume of a hydrocarbonsoluble carboxylic acid, and an amount of a liquid hydrocarbon-solvent sufficient to dissolve the pentacarbonyl and the acidified alkylesteralkylamide.

14. A stabilized iron pentacarbonyl concentrate consisting essentially of iron pentacarbonyl, from about i to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester-alkylamide of malic acid in which the hydroxy portion is free and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms,

. 7 the allwlester-alkylamide being acidified with no more than an equal volume oi a hydrocarbonsoluble carboxylic acid, and an amount oi a liquid hydrocarbon solvent suflicient to dissolve the pentacarbonyland the -acidified alkylester alkylamide.

15. A stabilized iron pentacarbonyl concentrate consisting essentially of iron pentacarbonyl, from about 1 to about 50% by volume on the pentacarbonyl of an acidified hydrocarbon-soluble neutral alkylester-alkylamide oi tartaric acid in which the hydroxy portion is free and the alkyl radical of each of the ester and amide groups in each instance contains at least 4 carbon atoms, the alkylester-alkylamide being acidified with no more than an equal volume of a hydrocarbonsoluble carboxylic acid, and an amount of'a liquid hydrocarbon solvent sufiicient to dissolve the pentacarbonyl and the acidified allwlesteralkylamide.

Number 8 16. A stabilized iron pentacarbonyl concentrate consisting essentially of iron pentacarbonyl, from about 1 to about 50% by volume on the pentacarbonyl of malic acid neutral oleylester-oleylamide acidified with a volume of a long chain fatty acid not exceeding that of the malic acid neutral oleylester-oleylamide and "an amount oi a liquid hydrocarbon solvent sufficient to dissolve the pentacarbonyl and the acidified malic acid neutral oleylester-oleylamide.

ROBERT EDWARD CHRIST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Lamping Feb. 28, 1939 

1. A COMPOSITION COMPRISING IRON PENTACARBONYL BLENDED WITH FROM ABOUT 1 TO ABOUT 50% BY VOLUME ON THE PENTACARBONYL OF AN ACIDIFIED HYDROCARBON-SOLUBLE NEUTRAL ALKYLESTER-ALKYLAMIDE OF A SATURATED ALIPHATIC HYDROXY POLYCARBOXYLIC ACID IN WHICH THE HYDROXY PORTION IS FREE AND THE ALKYL RADICAL OF EACH OF THE ESTER AND AMIDE GROUPS IN EACH INSTANCE CONTAINS AT LEAST 4 CARBON ATOMS, THE ALKYLESTER-ALKYLAMIDE BEING ACIDIFIED WITH NO MORE THAN AN EQUAL VOLUME OF A HYDROCARBON-SOLUBLE CARBOXYLIC ACID. 